|PRAGER, SEAN - University Of California|
|TRUMBLE, JOHN - University Of California|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2015
Publication Date: 11/1/2015
Citation: Prager, S.M., Wallis, C.M., Trumble, J.T. 2015. Indirect effects of one plant pathogen on the transmission of a second pathogen and the behavior of its potato psyllid vector. Environmental Entomology. 44:1065-1075.
Interpretive Summary: Plants encounter multiple biotic threats in the field, but limited research has been conducted to examine how these threats affect each other as mediated by host defense responses. Such knowledge will be crucial in development of comprehensive integrated pest management programs, as plant responses to one pest may affect predisposition to others. To this end, tomato-potato psyllid behaviors were monitored on tomato plants left uninfected or previously infected with Tobacco mosaic virus (TMV). The capacity of tomato-potato psyllids to successfully inoculate ‘Candidatus Liberibacter solanacearum’ (Lso) also was measured. Psyllids preferred non-infected plants to TMV-infected plants in choice assays, and Lso-transmission to non-infected plants was greater than to plants that were TMV-infected. These results demonstrated that TMV infection of tomato affected psyllid behaviors and reduced Lso infection success. As a result, future studies can commence to determine whether viral infections consistently reduce activities of similar insects and transmission of associated bacterial pathogens.
Technical Abstract: Plant pathogens can influence the behavior and performance of insect herbivore vectors. Studies of these associations typically focus on tripartite interactions between a plant host, a plant pathogen, and its insect vector. However, an unrelated herbivore or pathogen also could influence host-pathogen-vector interactions. Interactions between plant pathogens and insect pests were often found associated with changes in plant physiology, especially shifts in putative host defense chemistry. This study used a model system consisting of Tobacco mosaic virus (TMV), the tomato-potato psyllid (Bactericera cockerelli), and tomato to investigate multi-partite interactions between a pathogen, a non-vector, and a plant host, and observed whether or not shifts in host physiology affected these interactions. In addition, the ability of TMV to affect the success of another pathogen, ‘Candidatus Liberibacter solanacearum’, which is vectored by the psyllid, also was studied. Psyllids were observed to prefer non-infected plants to those infected with TMV in choice bioassays. No-choice bioassays demonstrated that, despite greater observed oviposition on control plants, there was no difference in psyllid development between infected and control plants. Following inoculation by psyllids, ‘Candidatus Liberibacter solanacearum’ titers were less in TMV-infected plants than TMV-free plants. TMV-infected plants had lower levels of amino acids and sugars, and few changes to levels of specific phenolics and terpenoids, relative to plants that were not infected with TMV. Likely because of these physiological changes, psyllid attractiveness was reduced in TMV-infected tomatoes and therefore decreased transmission and infection success of ‘Candidatus Liberibacter solanacearum’ occurred.